textproduct: Quad Cities

KEY MESSAGES

- Another system to pass through the area, bringing the chance for afternoon showers/storms along a passing cold front. A few storms may be strong to severe.

- A stretch of quiet and mostly dry weather will be seen this weekend and into next week, with seasonal temperatures.

SHORT TERM /THROUGH TONIGHT/

Issued at 140 AM CDT Fri Aug 21 2026

Shortwave trof to pass overhead today, dragging a cold front through the area from northwest-southeast this afternoon and evening. Prior to frontal passage, a pre-frontal wave will pass through this morning. This will bring along low-end chances for showers/storms (15-30% in our north), but coverage should largely remain isolated-scattered. Severe weather is not expected with this initial round of showers this AM. The chance for strong to severe storms will be focused along and ahead of the passing cold front this afternoon/evening. Although, uncertainty does exist on this threat. Compared to previous forecast packages, the front may come through a little earlier. This would generally put the timing of frontal passage between 12-8 PM locally. The earlier the front moves through may limit some of the destabilization, along with any residual cloud cover from decaying AM convection. Favored areas for storms will be along and east of the Mississippi River, with better chances over western Illinois.

Destabilization will be important for convective initiation, especially since shear is lacking (around 30 KTs deep layer shear). Short term guidance would favor 2000-3000 CAPE building by mid afternoon, which would be sufficient for some stronger storms, with sufficient lapse rates present. If strong to severe storms develop, damaging wind gusts would be the main concern, with large hail being secondary. There will also be a low-end tornado threat, largely for areas east of the Mississippi River, where low level hodographs have sufficient curvature to support it. Although, this should be a relatively isolated threat, coverage-wise. SPC continues to highlight much of the area in a Marginal Risk, level 1/5, for severe weather. Although, they have upgraded all locations along/east of the Mississippi River to a Slight Risk, or level 2/5 risk. While higher confidence exists on the potential for scattered showers/storms, especially east of the Mississippi River, much uncertainty remains on the overall severe threat and coverage. Thorough mesoscale analysis through the day will provide a better idea on the scope of the severe threat.

Post-frontal airmass will kick in tonight, with mostly clear skies and light northwesterly winds. Temperatures will remain in the 60s throughout, with decreasing humidity and dry conditions for the rest of the night.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 140 AM CDT Fri Aug 21 2026

Through the remainder of the forecast period, we will remain dominated by upper level northwest flow. This will continue to usher shortwaves through the area, which will help dampen the ridge that is forecast to set up over the Rockies. Although, this pattern is not favorable for much moisture return. Thus, precipitation chances will remain limited through this timeframe, with passing clouds and shifting winds being the main signs of the passing waves. Temperatures will remain seasonal and hover around 80 degrees, with low humidity to make it quite pleasant. After Friday night, our precipitation chances will be quite limited. Some global models skirt our south with precipitation chances from a passing system on Monday, and then more widespread PoPs midweek, albeit low. Overall, chances for precipitation with both of these systems generally fall between 20-40%.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 619 AM CDT Fri Aug 21 2026

Mainly VFR weather will continue through today, though a cold front arriving this afternoon will bring a chance (20-50%) for storms to extreme eastern Iowa and northern Illinois each hour from 19z through 23z. This will be for DBQ and MLI, with other sites west and south remaining dry, with only a 20% chance for a shower or storm this afternoon/evening. Any storm this afternoon could bring a brief period of IFR visibility/strong winds/ and hail. After 00z, VFR weather is confidently forecast to return to the entire area.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.